---
name: "v.net.components"
section: "1grass"
platform: "linux"
package: "grass-doc"
version: "8.4.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/v.net.components"
---

# v.net.components(1grass)

Computes strongly and weakly connected components in the network.

## NAME

**v.net.components**  - Computes strongly and weakly connected components in the network.

## KEYWORDS

vector, network, components

## SYNOPSIS

**v.net.components**\
 **v.net.components --help**\
 **v.net.components** \[-**a**\] **input**=*name*  \[**arc\_layer**=*string*\]   \[**node\_layer**=*string*\]   \[**arc\_column**=*name*\]   \[**arc\_backward\_column**=*name*\]   \[**node\_column**=*string*\]  **output**=*name* **method**=*string*  \[--**overwrite**\]  \[--**help**\]  \[--**verbose**\]  \[--**quiet**\]  \[--**ui**\]

### Flags:

- **-a**

  Add points on nodes

- **--overwrite**

  Allow output files to overwrite existing files

- **--help**

  Print usage summary

- **--verbose**

  Verbose module output

- **--quiet**

  Quiet module output

- **--ui**

  Force launching GUI dialog

### Parameters:

- **input**=*name* **\[required\]**

  Name of input vector map\
   Or data source for direct OGR access

- **arc\_layer**=*string*

  Arc layer\
   Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.\
   Default: *1*

- **node\_layer**=*string*

  Node layer\
   Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.\
   Default: *2*

- **arc\_column**=*name*

  Arc forward/both direction(s) cost column (number)

- **arc\_backward\_column**=*name*

  Arc backward direction cost column (number)

- **node\_column**=*string*

  Node cost column (number)

- **output**=*name* **\[required\]**

  Name for output vector map

- **method**=*string* **\[required\]**

  Type of components\
   Options: *weak, strong*\
   **weak**: Weakly connected components\
   **strong**: Strongly connected components

## DESCRIPTION

*v.net.components* computes the weakly and strongly connected components in a network.

## NOTES

Two nodes, *u* and *v* are in the same strongly connected component if there are directed paths from *u* to *v* and from *v* to *u*. The nodes are in the same weakly connected component if, ignoring edge directions, there is a path between them.

The type of components is specified by **method** parameter. *v.net.components* creates a table and links it to layer 1. This table contains only two integer columns: *cat* and *comp*. If a point or both endpoints of a line belong to the same component then the point/line is written to the output map and appropriate information is stored in the table. If **-a** flag is set then new points are added on the nodes without points. These points have category numbers larger than any category used in the input map.

One-way roads can be defined by assigning a cost of -1 to the appropriate cost column (**arc\_column** or **arc\_backward\_column**). This affects only strongly connected components. Network nodes can be closed by assigning a cost of -1 to the node cost column. All nodes with a cost \< 0 can not be traversed and are end points, while all nodes with a cost ≥ 0 can be traversed. This affects both weakly and strongly connected components.

## EXAMPLES

Any road network should form a single strongly connected component. Otherwise, it is impossible to travel between some places.\

```
v.net.components input=roads output=roads_components method=strong
```

## SEE ALSO

*v.net,* *v.category*

## AUTHORS

Daniel Bundala, Google Summer of Code 2009, Student\
 Wolf Bergenheim, Mentor\
 Markus Metz

## SOURCE CODE

Available at: v.net.components source code (history)

Accessed: Monday Feb 24 17:51:18 2025

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